1. Field of the Invention
The present invention relates to a modified polyethylene or a modified polyethylene composition and a laminate which includes said modified polyethylene or said modified polyethylene composition. More particularly, the present invention relates to a modified polyethylene or a composition containing the modified polyethylene and a laminate including the modified polyethylene or the modified polyethylene composition.
2. Description of the Prior Art
Japanese unpatented publication Nos. 51-122152 (1976), 52-25845 (1977), and 50-4189 (1975) disclose (a) medium- and low-pressure high density polyethylene (HDPE) and high-pressure low density polyethylene (LDPE) modified with an unsaturated carboxylic acid or a derivative thereof and (b) a mixture of the modified polyethylene and unmodified polyethylene. These compositions are disclosed as being used to improve the corrosion resistance, external appearance, and food sanitation of metal pipes, or to remedy drawbacks inherent in metal pipes, metal plates, electric wires and cables, wires, and a variety of synthetic resins.
Modified polyethylenes obtained by modifying conventional HDPE or LDPE, or compositions containing modified polyethylene and unmodified polyethylene do not have a sufficient bond strength for metals such as steel and aluminum and thermoplastic resins such as nylon and vinylon. Such modified polyethylene compositions are poor in ESCR and toughness when used in the form of laminates formed by extrusion coating, powder coating, or coextrusion. Moreover, modified LDPE is poor in flowability because it has long branches and a broad molecular weight distribution. This drawback is not remedied even when LDPE having a high melt flow index (abbreviated as MI hereunder) is used as the base polymer. The poor flowability is detrimental to powder coating in which the molten resin should flow under no load.